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Static import in Java allows to import static members of class and use
them, as they are declared in the same class. Static import is introduced in
Java 5 along with other features like Generics,
Enum,
Autoboxing
and Unboxing and variable
argument methods. Many programmer think that using static import can reduce
code size and allow you to freely use static field of external class
without prefixing class name on that. For example without static import you will
access static constant MAX_VALUE of Integer class as Integer.MAX_VALUE but by
using static import you can import Integer.MAX_VALUE and refer
it as MAX_VALUE. Similar to regular import
statements, static import also allows wildcard * to import all static
members of a class. In next section we will see Java program to demonstrate
How to use static import statements to import static fields.

Difference between java.sql.Time, java.sql.Timestamp and java.sql.Dateis most common JDBC question appearing on
many core Java interviews. As JDBC
provides three classes java.sql.Date, java.sql.Time and java.sql.Timestamp to
represent date and time and you already have java.util.Date which can
represent both date and time, this question poses lot of confusion among Java
programmer and that’s why this is one of those tricky
Java questions which is tough to answer. It becomes really tough if
differences between them is not understood correctly. We have already seen some
frequently asked or common JDBC questions like why
JDBC has java.sql.Date despite java.util.Date and Why
use PreparedStatement in Java in our last tutorials and we will see
difference between java.sql.Date, java.sql.Time and java.sql.Timestamp in this
article. By the way apart from these JDBC interview questions, if you are
looking to get most from JDBC you can also see 4
JDBC performance tips and 10
JDBC best practices to follow. Those article not only help you to
understand and use JDBC better but also help on interviews. Let’s come back to
difference sql time, timestamp and sql date.

JSTL foreach tag is pretty useful
while writing Java free JSP code. JSTL
foreach tag allows you to iterate or loop
Array List, HashSet
or any other collection without using Java code. After introduction of JSTL and
expression language(EL) it is possible to write dynamic JSP code without using
scriptlet which clutters jsp pages. JSTL
foreach tag is a replacement of for loop and behaves similarly like foreach
loop of Java 5 but still has some elements and attribute which makes it hard
for first-timers to grasp it. JSTL foreach loop can iterate over arrays,
collections like List,
Set
and print values just like for loop. In this JSP tutorial we will see couple of
example of foreach loop which makes it easy for new guys to understand and use
foreach loop in JSP. By the way this is our second JSP tutorial on JSTL core
library, in last tutorial we have seen How
to use core <c:set> tag in JSP page.

Eclipse IDE provides quick shortcut keys to print System.out.println statement in Java but unfortunately not every Java programmers are familiar of that. Even programmers with 3 to 4 year of experience sometimes doesn't know this useful Eclipse shortcut to generate System.out.println messages. This Eclipse tips is to help those guys. Let me ask you one question, How many times you type System.out.println in your Java program? I guess multiple time, while doing programming, debugging and testing small stuff. System.out.println is the most preferred way to print something on console because it doesn’t required setup like configuring Log4J or java.util.Logger . Though I recommend usinglogging for better information display in production code, nobody can undermine importance of System.out.println statement in Java. On the quest of learning Eclipse shortcut, some of them which I have discussed in my list of Top 30 Eclipse shortcut for Java programmers, I found a very useful Eclipse shortcut for generating code for System.out.println statement in Java source file.

Write a Java program to calculate
Area of Triangle, accept input from User and display output in Console is
one of the frequently asked homework question. This is not a tough
programming exercise but a good exercise for beginners and anyone who has
started working in Java. For calculating area of triangle using formula 1/2(base*height), you need
to use arithmetic operator. By doing this kind of exercise you will understand
how arithmetic operators works in Java, subtle details which affect calculation
like precedence and associativity of operator etc. Fortunately this question
is not very popular on Java
interview like other exercise we have seen e.g. Java
program to print Fibonacci series and Java
program to check for palindrome. Nevertheless its a good Java homework.

Adding JAR into classpath is a common task for Java programmer and different programmer do it on different way. Since Java allows multiple ways to include JAR file in classpath, it becomes important to know pros and cons of each approach and How exactly they work. There are 5 ways to add jars on into classpath in Java some of them we have already seen in How classpath works in Java and How to set Path in Java. In this post we will revisit some of those techniques and explore Java 1.6 wildcard to add multiple JAR into classpath. By the way here is 5 ways to add JAR file into classpath. In short knowledge of Path, Classpath and Classloaders are must for any Java programmer, not only from knowledge point of view but also to successfully debug and resolve issues related to Classpath e.g. NoClassDefFoundError and java.lang.ClassNotFoundExceptionin Java.

In order to build a regular expression to check if String is number or
not or if Stringcontains any non digit
character or not you need to learn about character set in Java regular
expression, Which we are going to see in this Java regular expression example.
No doubt Regular Expression is great
tool in developer arsenal and familiarity or some expertise with regular
expression can help you a lot. Java supports regular expression using java.util.regex.Pattern and java.util.regex.Matchter class, you
can see a dedicated packagejava.util.regex for
regular expression in Java. Java supports regex from JDK 1.4, means well before
Generics, Enum or Autoboxing. If you are writing server side code in Java
programming language than you may be familiar with importance of regular
expression which is key in parsing certain kind of messages e.g. FIX Messagesused in
Electronic trading. In order to parse Repeating groups in FIX protocol
you really needs understanding of regular expression in Java. Any way In order
to learn validating numbers using regular expression we will start with simple
example

Java has four access modifier namely private, protected and public. package level access is default access level provided by Java if no access modifier is specified. These access modifiers are used to restrict accessibility of a class, method or variable on which it applies. We will start from private access modifier which is most restrictive access modifier and then go towards public which is least restrictive access modifier, along the way we will see some best practices while using access modifier in Java and some examples of using private and protected keywords.

Garbage collection interview questions are very popular in both core Java and advanced Java Interviews. Apart from Java Collection and Threadmanytricky Java questions stems Garbage collections which are tough to answer. In this Java Interview article I will share some questions from GC which is asked in various core Java interviews.These questions are based upon concept of How Garbage collection works, Different kinds of Garbage collector and JVM parameters used for garbage collection monitoring and tuning. As I said GC is an important part of any Java interview so make sure you have good command in GC. One more thing which is getting very important is ability to comprehend and understand Garbage collection Output, more and more interviewer are checking whether candidate can understand GC output or not. DuringJava interviewthey may provide a snippet of GC output and ask various questions based on that e.g. Which Garbage collector is used, whether output is from major collection or minor collection, How much memory is free from GC, What is size of new generation and old generation after GC etc. I have included few Garbage collection interview questions and answers from GC output to help with that. It’s recommended to prepare questions from Java collection,multithreading and programmingalong with Garbage collection to do well in Java interviews at any stage.

How to get input from user in Java from command line or console is one of the common thing
,every one started learning Java looks for. It’s second most popular way of
starting programming after HelloWorld
in Java. There are so many ways to get input from User in Java including
command line and Graphical user interface. For beginner simpler the example,
better it is. first and foremost way of getting input from user is String[]
passed to main
method in Java but that only work for one time requirement and its not
interactive. Another way of getting input from User is involving IO classes
like InputStream
to read from console or command line which can be little complicated for true
beginner. Thanks to Java 5 which added a nice utility class called Scanner, has made
task of getting input from user very easy. Scanner is
powerful and allows you to get any kind of input from User e.g. String,
int,
float etc.

Eclipse IDE gives warning "The import XXX is never used" whenever it detect unused import in Java source file and shows a yellow underline. Though unused import in Java file does not create any harm, it's unnecessary increase length and size of Java source file and if you have too many unused imports in your Java source file, those yellow underline and Eclipse warning affect readability and working. In our last post on Eclipse, we have seen dome Java debugging tips on Eclipse and in this post we will see Eclipse shortcut to remove all unused imports in Eclipse. There are many options to tackle this problem e.g. you can collapse import section of code in Eclipse or you can altogether remove all unused imports from Java file. Since Eclipse is favorite IDE of many Java programmer, who love to do things fast in shortcuts, I will also share Eclipse shortcut to remove unused imports from Java program in this article. This is one of many Eclipse shortcuts which we have discussed in our post Top 30 Eclipse keyboard shortcut for Java programmer. Let's see How to remove all unused imports from Java file in Eclipse IDE.

10 Java String interviews Question answers
String interview questions in Java is one of Integral part of any Core Java or J2EE interviews. No one can deny the importance of String and how much it is used in any Java application irrespective of whether its core Java desktop application, web application, Enterprise application or Mobile application. The string is one of the fundamental of Java programming language and correct understanding of String class is a must for every Java programmer. What makes String interview questions in Java even more interesting is the special status of String in terms of features and privileges it has, like the + operator is kind of overloaded to perform String concatenation despite the fact that Java does not support operator overloading. There is a separate String pool to store String literal etc.

Inheritance in Java is an Object oriented or OOPS
concepts, which allows to emulate real world Inheritance behavior, Inheritance
allows code reuse in Object oriented programming language e.g. Java. Along with
Abstraction,
Polymorphism
and Encapsulation,
Inheritance forms basis of Object oriented programming. Inheritance is
implemented using extends keyword in Java and When one
Class extends another Class it inherit all non
private members including fields and methods. Inheritance in Java can be
best understand in terms of Parent and Child class,
also known as Super class and Sub class in Java programming language. The class
which extends another class becomes Child of the class it extends and
inherit all its functionality which is not private or package-private given
where Child class is created. Inheritance is the
most easy way to reuse already written and tested code but not always best way
to do so, which we will see in this article. There are lot of example of
Inheritance in Object oriented world e.g. Child inherit properties from parent,
Dog inherit properties of Animal etc. In this Java and OOPS
tutorial we will learn What is Inheritance in Java, How to use
Inheritance in Java, Simple Example of
Java Inheritance and some important points about Inheritance in Java.